1. Field of the Invention
The present invention relates to an elastic member for ink jet such as an ink seal or a rubber stopper used for an ink storage portion and an ink flow path portion.
2. Description of the Related Art
As an elastic member used for an ink storage portion and an ink flow path of an ink jet recording head, a sealing part or a rubber stopper can be mentioned, for example. As a material for the elastic member, a thermoplastic elastomer is generally used. Further, in an ink jet application, water vapor barrier properties for preventing ink evaporations, air barrier properties for suppressing bubbles from entering, rubber elasticity for and flexibility (low hardness) ensuring sealing properties, and the like are required as disclosed in Japanese Patent Application Laid-Open No. 2005-305878. In addition, the ink jet recording head flies very fine droplets, and hence a nozzle for ejecting ink has a diameter as small as, for example, 10 μm or less in some cases. Therefore, when a foreign material with a size of several μm is discharged from an elastic member that constructs an ink flow path, the foreign material may inhibit ink from being ejected and cause printing failure. Accordingly, a compound that constructs an elastic member for ink jet needs to have liquid-contact properties of being dissolved without causing precipitation even when eluted in ink, and it is necessary to suppress the compound from being discharged as a foreign material without being dissolved in ink to a possible extent.
Further, the thermoplastic elastomer generally has low releasability during injection molding, and hence cannot be molded in some cases due to its unreleasability. Of the thermoplastic elastomers, a material having a low hardness and high barrier properties tends to have particularly low releasability, and hence a thermoplastic elastomer having physical properties required for an ink jet application often has low releasability. Therefore, a release agent is required during molding in most cases. The release agent is broadly classified into an external release agent and an internal release agent. The external release agent is used by being directly applied to a mold. Although it is easy to treat a mold with the external release agent, an effect of the release agent is gradually reduced, and hence it is necessary to apply the release agent every time the effect is reduced. On the other hand, the internal release agent is used by being kneaded into a material in advance. The use of a material blended with the internal release agent has advantages of saving the trouble of application of the release agent to a mold and not causing a reduction in release effect even after repeated molding.